One year ago, the Aegis Ashore ballistic missile defense site in Deveselu, Romania, achieved initial operational capability. While protection from a limited missile strike from outside the Euro-Atlantic area remains fundamental to the security of NATO, new threats have emerged and need to be addressed.

Russian anti-access, area denial, or A2AD, bubbles in the Kaliningrad enclave and on the Crimean Peninsula restrict NATO's self-defense capabilities. In particular, the presence of long-range surface-to-air systems (S-300, S-400, S300V4) keeps NATO air forces over the Baltic and Black seas in check, restricting the freedom of movement of allied troops. This includes U.S. Army personnel forward deployed across NATO's eastern flank as part of the European Reassurance Initiative.

Two NATO members, Poland and Romania, are particularly concerned and are taking action. Both have ongoing Foreign Military Sales cases for the Patriot air-and-missile defense system, and both agreed to host the U.S. Navy's Aegis Ashore system on their soil.

Russian AAW

However, in currently assumed configurations, neither of those systems is capable of providing adequate response to the Kremlin's A2AD strategy. Consider the parameters of Russian extended-range anti-air warfare, or AAW, interceptors. For example, the S400 system currently operates the 48N6 family of missiles, over 7 meters in length and 21 inches in diameter. The manufacturer, Fakel, claims the missile's engagement envelopes a reach of 250 kilometers. Even more impressive would be the soon-to-be-fielded 40N6 missile, which is equipped with active radar homing, or ARH, guidance and has an estimated range of 400 kilometers.

Fakel's claims are unverified and likely exaggerated. For example, ground-based sensors of these systems are physically restricted by the horizon, limiting awareness of even ARH-equipped missiles. Nonetheless, it is safe to say that Russian AAW capability outmatches NATO assets on the ground in Eastern Europe.

Allied capabilities: Patriot and Aegis

On the other hand, NATO's most common medium-range ground-based air defense system, the Patriot, was designed for point area defense at shorter distances. The PAC-2 GEM-T missile, widely used for tactical ballistic missile protection, is also best equipped for extended-range AAW. However, with a length of 5.2 meters and a diameter of 16 inches, the GEM-T uses track-via-missile guidance and is horizon-limited to about a 160-kilometer range. Romania will likely procure GEM-T missiles to fill its four to seven Patriot fire units. Poland, however, decided to forgo GEM-T altogether and arm its 16 fire units solely with even shorter-range SkyCeptor and PAC-3 MSE missiles.

Aegis Ashore is part of the European Phased Adaptive Approach, or EPAA — the U.S. national contribution to the NATO missile defense system. Its purpose is to counter a limited, short- to medium-range ballistic missile attack from outside the Euro-Atlantic area. As such, the Polish and Romanian sites are armed only with variants of the exo-atmospheric SM-3 missile and do not possess any capability against threats operating below the altitude of 100 kilometers, like most aircraft.

Consequently, Russia can freely engage targets above much of the Black Sea and most of Poland, while NATO cannot respond in kind.

Adapting the Aegis Ashore

The balance could be restored by expanding the missile arsenal of Aegis Ashore's sites in Poland and Romania. EPAA bases contain Mark 41 launchers with 24 ready-to-fire missiles per site. The system could be upgraded to include AAW capabilities available to its maritime progenitor — Mk 41 cells can launch, inter alia, SM2, SM6 and ESSM interceptors. Of the above, the SM-6 is most potent and versatile, reaching targets 460 kilometers away. Notably, Congress already obliged the U.S. Department of Defense to explore a possibility of adding AAW to EPAA.

Russia's objections

Russia is sure to object furiously to any new military deployments in what it considers to be its sphere of influence. A supposedly destabilizing nature of missile defenses is one, often used argument. The hypocrisy is clear considering Russia's military ventures in the last couple of months alone.

Kaliningrad, which already hosts three regiments of S-300s, a regiment of S-400s and numerous other offensive missile systems, was reinforced with the anti-ballistic S-300V4 system in April. Moreover, the Pentagon recently confirmed that Russia violated "spirit and intent" of the Intermediate-Range Nuclear Forces Treaty in regard to unspecified systems, while the SS-26 Iskander-K cruise missile might also breach GLCM's allowable 500-kilometer limit. Finally, in early April, the Russian Navy conducted a submarine-launched cruise missile test, striking targets on the Baltic Sea. Therefore, Kremlin's actions hardly amount to sowing stability.

A balanced response

Placing half a dozen or so AAW interceptors in Aegis Ashore sites will be no match to Russia's deployments in Kaliningrad or Crimea. This holds true even if more than three Mk 41 launchers were to be installed to enable the AAW capability.

The sites are stationary, making them easy to target and destroy by a saturating missile strike. Therefore, AAW will not cancel Russia's tactical advantages in Eastern Europe, let alone undermine the Kremlin's strategic deterrence capabilities.

It will, however, change the calculus for provocative actions that Russia might undertake to test NATO's resolve. Inability to maneuver freely in the regional airspace will heavily impact Russia's military planning and restrict opportunities for provocative endeavors. Therefore, NATO, as the integrator of national member-state assets, should encourage the United States to add AAW capabilities to Aegis Ashore sites in Poland and Romania.

Maciej Kowalski is a research fellow at the Casimir Pulaski Foundation, which specializes in foreign policy and international security.